For example, particulate collection devices using various filters that are called DPD (registered trade name, Diesel Particulate Defuser) are used to collect a particulate matter (referred to hereinbelow as PM) contained in exhaust gas discharged from a diesel engine.
Where the filter is clogged by the collected PM in such a collection device, the exhaust gas is difficult to discharge. Therefore, the filter is regenerated by oxidizing and removing (combusting) the collected PM.
Active regeneration systems such as electric heating, burner combustion, and fuel addition and self-regenerating (also called passive) regeneration systems are known as DPD regeneration systems.
With an active regeneration system, a driver starts the regeneration by operating a switch. Therefore, the driver has to be notified about the degree to which PM has been accumulated in the filter.
Accordingly, a display device is known that displays an amount of PM collected in the filter.
For example, Japanese Patent Application Laid-Open No. 2000-24440 suggests a configuration in which a warning lamp is lit up correspondingly to the collected amount of PM and a configuration in which six LEDs representing a multistage warning unit are successively lit up when PM collection and regeneration of DPD are performed.
Furthermore, the collected amount of PM or regeneration state of DPD is displayed by lighting up or blinking the warning lamp and changing the blinking speed and interval.